Poly(arylene sulfides) (hereinafter abbreviated as “PASs”) represented by poly(phenylene sulfide) (hereinafter abbreviated as “PPS”) are an engineering plastics excellent in heat resistance, chemical resistance, flame retardancy, mechanical properties, electrical properties, dimensional stability and the like. The PASs are commonly used in wide fields such as electrical and electronic equipments and automotive equipments because they can be formed or molded into various kinds of molded or formed products, films, sheet, fibers, etc. by general melt processing techniques such as extrusion, injection molding and compression molding.
As a typical production process of PAS, is known a process in which a sulfur source is reacted with a dihalo-aromatic compound in an organic amide solvent such as N-methyl-2-pyrrolidone. There is known a method of using an alkali metal hydrosulfide and an alkali metal hydroxide in combination as materials for the sulfur source. However, this method is difficult to set conditions for stably performing a polymerization reaction. In addition, according to this method, difficulty is encountered on inhibition of side reactions, the content of volatile matter becomes great, and difficulty is encountered on reduction in the content of bis(4-chlorophenyl) sulfide that is an impurity due to a great amount of the alkali metal hydroxide used upon the polymerization reaction.
There has heretofore been proposed a production process of PAS, in which an alkali metal hydrosulfide, an alkali metal hydroxide and a polyhalo-aromatic compound are reacted by 2 stages (for example, Japanese Patent Application Laid-Open Nos. 2-302436 and 5-271414). In Japanese Patent Application Laid-Open No. 2-302436, it is described that the amount of the alkali metal hydroxide used is within a range of 0.7 to 1.3 mol, preferably 0.9 to 1.1 mol per mol of the alkali metal hydrosulfide. In Examples of Japanese Patent Application Laid-Open No. 2-302436, is shown an experimental example that sodium hydroxide was used in a proportion of 0.92 mol per mol of sodium hydrosulfide. Japanese Patent Application Laid-Open No. 5-271414 also disclose a like technical matter.
According to these processes, however, it is difficult to reduce the content of bis(4-chlorophenyl) sulfide and also to improve the reactivity to silane coupling agents. In addition, there is a tendency to make it difficult to stably perform a polymerization reaction and to fail to produce a high-molecular weight polymer at high yield when the molar ratio of sodium hydroxide used to sodium hydrosulfide is low as shown in Examples of these documents. Japanese Patent Application Laid-Open No. 2-302436 describes the fact that the amount of gases generated is small, but does not show analytical results as to gas compositions.
There has been proposed a production process of poly(p-phenylene) sulfide, in which a molar ratio of an alkali metal hydroxide to an alkali metal hydrosulfide is controlled to 0.80:1 to 0.98:1 to conduct polymerization by one stage (for example, Japanese Patent Publication No. 6-51792). According to this process, however, side reactions are easy to occur, difficulty is encountered on stably performing a polymerization reaction, and moreover it is also difficult to reduce the content of bis(4-chlorophenyl) sulfide and to improve the reactivity to silane coupling agents.
There has been proposed a production process of PAS, in which an alkali metal hydroxide is used in a proportion amounting to at most 1 mol per mol of an alkali metal hydrosulfide to conduct polymerization by one stage (for example, Japanese Patent Application Laid-Open No. 2001-181394). There has also been proposed a production process of PAS by one stage by using an alkali metal hydrosulfide and an alkali metal hydroxide to specify a molar ratio between the respective components (for example, Japanese Patent Application Laid-Open No. 2-160834). There has further been proposed a process for producing PAS by one stage by controlling the amount of an alkali metal hydroxide added to 0.3 to 4 mol per mol of an alkali metal hydrosulfide (for example, Japanese Patent Publication No. 6-51793). However, these processes also involve the same problems as in Japanese Patent Publication No. 6-51792.